DDAH-1 maintains endoplasmic reticulum-mitochondria contacts and protects dopaminergic neurons in Parkinson's disease.

The loss of dopaminergic neurons in the substantia nigra is a hallmark of pathology in Parkinson's disease (PD). Dimethylarginine dimethylaminohydrolase-1 (DDAH-1) is the critical enzyme responsible for the degradation of asymmetric dimethylarginine (ADMA) which inhibits nitric oxide (NO) synthase and has been implicated in neurodegeneration. Mitochondrial dysfunction, particularly in the mitochondria-associated endoplasmic reticulum membrane (MAM), plays a critical role in this process, although the specific molecular target has not yet been determined. This study aims to examine the involvement of DDAH-1 in the nigrostriatal dopaminergic pathway and PD pathogenesis. The distribution of DDAH-1 in the brain and its colocalization with dopaminergic neurons were observed. The loss of dopaminergic neurons and aggravated locomotor disability after rotenone (ROT) injection were showed in the DDAH-1 knockout rat. L-arginine (ARG) and NO donors were employed to elucidate the role of NO respectively. In vitro, we investigated the effects of DDAH-1 knockdown or overexpression on cell viability and mitochondrial functions, as well as modulation of ADMA/NO levels using ADMA or ARG. MAM formation was assessed by the Mitofusin2 oligomerization and the mitochondrial ubiquitin ligase (MITOL) phosphorylation. We found that DDAH-1 downregulation resulted in enhanced cell death and mitochondrial dysfunctions, accompanied by elevated ADMA and reduced NO levels. However, the recovered NO level after the ARG supplement failed to exhibit a protective effect on mitochondrial functions and partially restored cell viability. DDAH-1 overexpression prevented ROT toxicity, while ADMA treatment attenuated these protective effects. The declines of MAM formation in ROT-treated cells were exacerbated by DDAH-1 downregulation via reduced MITOL phosphorylation, which was reversed by DDAH-1 overexpression. Together, the abundant expression of DDAH-1 in nigral dopaminergic neurons may exert neuroprotective effects by maintaining MAM formation and mitochondrial function probably via ADMA, indicating the therapeutic potential of targeting DDAH-1 for PD.

A myzozoan-specific protein is an essential membrane-anchoring component of the succinate dehydrogenase complex in Toxoplasma parasites.

Succinate dehydrogenase (SDH) is a protein complex that functions in the tricarboxylic acid cycle and the electron transport chain of mitochondria. In most eukaryotes, SDH is highly conserved and comprises the following four subunits: SdhA and SdhB form the catalytic core of the complex, while SdhC and SdhD anchor the complex in the membrane. Toxoplasma gondii is an apicomplexan parasite that infects one-third of humans worldwide. The genome of T. gondii encodes homologues of the catalytic subunits SdhA and SdhB, although the physiological role of the SDH complex in the parasite and the identity of the membrane-anchoring subunits are poorly understood. Here, we show that the SDH complex contributes to optimal proliferation and O2 consumption in the disease-causing tachyzoite stage of the T. gondii life cycle. We characterize a small membrane-bound subunit of the SDH complex called mitochondrial protein ookinete developmental defect (MPODD), which is conserved among myzozoans, a phylogenetic grouping that incorporates apicomplexan parasites and their closest free-living relatives. We demonstrate that TgMPODD is essential for SDH activity and plays a key role in attaching the TgSdhA and TgSdhB proteins to the membrane anchor of the complex. Our findings highlight a unique and important feature of mitochondrial energy metabolism in apicomplexan parasites and their relatives.

In vivo and in vitro studies on the role of regulating Smac expression in the occurrence and development of colon cancer.

We aimed to explore the role of regulating Smac expression levels in the occurrence and development of colon cancer through in vitro and in vivo experiments. Colon cancer cells HT-29 were cultured and transfected into different groups. qRT-PCR was used to detect the expression level of Smac in cells; Flow cytometry was used to detect the apoptotic ability of each group of cells; Western blot was used to detect the protein expression of Smac and apoptosis-related factors Survivin and Caspase-3; The nude mouse tumorigenesis experiment was conducted to detect the regulatory effect of regulating Smac expression levels on the growth of colon cancer transplanted tumors in vivo. In comparison to the FHC group, the HT-29 group exhibited a decrease in Smac expression. The si-Smac group, when compared with the si-NC group, showed significant reductions in Smac mRNA and protein levels, weaker cell apoptosis, increased Survivin, and decreased Caspase-3 expression. Contrarily, the oe-Smac group, against the oe-NC group, displayed increased Smac mRNA and protein levels, enhanced apoptosis, reduced Survivin, and elevated Caspase-3 expression. In nude mice tumor transplantation experiments, the LV-sh-Smac group, as opposed to the LV-sh-NC group, had tumors with greater volume and weight, reduced Smac and Caspase-3, and increased Survivin expression. In contrast, the LV-oe-Smac group, compared with the LV-oe-NC group, showed tumors with decreased volume and mass, increased expressions of Smac and Caspase-3, and decreased Survivin. Smac is lowly expressed in colon cancer. Upregulation of Smac expression can inhibit the occurrence and development of colon cancer, possibly by inhibiting Survivin expression and promoting Caspase-3 expression, thereby enhancing the pro-apoptotic function.

Developmental dynamics of mitochondrial fission and fusion proteins in functionally divergent skeletal muscles of goat.

During skeletal muscle development, the intricate mitochondrial network formation relies on continuous fission and fusion. This process in larger mammals differs from rodents, the most used animal models. However, the expression pattern of proteins regulating mitochondrial dynamics in developing skeletal muscle remains unexplored in larger mammals. Therefore, we characterized the cellular expression and tissue-level distribution of these proteins during development taking goat as a model. We have performed histological and immunohistochemical analyses to study metabolic features in various muscles. Neonatal muscles display uniform distribution of mitochondrial activity. In contrast, adult muscles exhibit clear distinctions based on their function, whether dedicated for posture maintenance or facilitating locomotion. Mitochondrial fission proteins like DRP-1, MFF, and fusion proteins like MFN-1 and 2 are abundantly expressed in neonatal muscles. Fission proteins exhibit drastic downregulation with limited peripheral expression, whereas fusion proteins continue to express in a fiber-specific manner during adulthood. Locomotory muscles exhibit different fibers based on mitochondrial activity and peripheralization with high SDH activity. The proximity ligation assay between MFN1 and MFN2 demonstrates that their interaction is restricted to subsarcolemmal mitochondria in adult fibers while distributed evenly in neonatal fibers. These differences between postural and locomotory muscles suggest their physiological and metabolic properties are different.

Suppressing mitochondrial inner membrane protein (IMMT) inhibits the proliferation of breast cancer cells through mitochondrial remodeling and metabolic regulation.

Metabolic reprogramming is widely recognized as a hallmark of malignant tumors, and the targeting of metabolism has emerged as an appealing approach for cancer treatment. Mitochondria, as pivotal organelles, play a crucial role in the metabolic regulation of tumor cells, and their morphological and functional alterations are intricately linked to the biological characteristics of tumors. As a key regulatory subunit of mitochondria, mitochondrial inner membrane protein (IMMT), plays a vital role in degenerative diseases, but its role in tumor is almost unknown. The objective of this research was to investigate the roles that IMMT play in the development and progression of breast cancer (BC), as well as to elucidate the underlying biological mechanisms that drive these effects. In this study, it was confirmed that the expression of IMMT in BC tissues was significantly higher than that in normal tissues. The analysis of The Cancer Genome Atlas (TCGA) database revealed that IMMT can serve as an independent prognostic factor for BC patients. Additionally, verification in clinical specimens of BC demonstrated a positive association between high IMMT expression and larger tumor size (> 2 cm), Ki-67 expression (> 15%), and HER-2 status. Furthermore, in vitro experiments have substantiated that the suppression of IMMT expression resulted in a reduction in cell proliferation and alterations in mitochondrial cristae, concomitant with the liberation of cytochrome c, but it did not elicit mitochondrial apoptosis. Through Gene Set Enrichment Analysis (GSEA) analysis, we have predicted the associated metabolic genes and discovered that IMMT potentially modulates the advancement of BC through its interaction with 16 metabolic-related genes, and the changes in glycolysis related pathways have been validated in BC cell lines after IMMT inhibition. Consequently, this investigation furnishes compelling evidence supporting the classification of IMMT as prognostic marker in BC, and underscoring its prospective utility as a novel target for metabolic therapy.

Peripheral blood mononuclear cells show markers of mitochondrial dysfunction in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease. Metabolic and mitochondrial dysregulation are critical causal factors in the pathogenesis and progression of RA. Mitochondrial dysfunction include abnormal energy metabolism, and excessive production of reactive oxygen species (ROS). This study aimed to investigate the adenosine triphosphate (ATP), mitochondrial membrane potential (ΔΨm), ROS, and mRNA expression level of ROMO1 (as ROS modulator) and OMA1 (as regulator mitochondrial dynamics) of peripheral blood mononuclear cells (PBMC) in RA patients. The study participants were 50 patients with RA and 50 sex- and age-matched healthy volunteers. PBMC of all participant were isolated by Ficoll-Paque. Alteration in ΔΨm and cellular ROS were measured using flow cytometry, ATP level was also assessed via luminometry, and ROMO1 and OMA1 mRNA expression via qRT-PCR assay. A significant decrease in ATP (p = .005) and ΔΨm (p < .001) was observed in the PBMC of RA compared to control. The ROS levels were significantly higher in the PBMC of RA compared to the control (p < .001). ROMO1 and OMA1 mRNA expression was also significantly increased in RA patients compared to control (p < .001). The decrease in ATP is strongly associated with ROS increasing in PBMC of RA patients, denoting an inverse and negative relationship between ATP and ROS production. Also, a decrease in ΔΨm was observed. It seems that in line with mitochondrial dysfunction in PBMC, increased expression of ROMO1 and OMA1 genes could also be involved in the development of RA.

Mitochondrial alternative oxidase pathway helps in nitrooxidative stress tolerance in germinating chickpea.

Mitochondrial alternative oxidase (AOX) is an important protein that can help in regulating reactive oxygen species and nitric oxide in plants. The role of AOX in regulation of nitro-oxidative stress in chickpea is not known. Using germinating chickpea as a model system, we investigated the role of AOX in nitro-oxidative stress tolerance. NaCl treatment was used as an inducer of nitro-oxidative stress. Treatment of germinating seeds with 150 mM NaCl led to reduced germination and radicle growth. The AOX inhibitor SHAM caused further inhibition of germination, and the AOX inducer pyruvate improved growth of the radicle under NaCl stress. Isolated mitochondria from germinated seeds under salt stress not only increased AOX capacity but also enhanced AOX protein expression. Measurement of superoxide levels revealed that AOX inhibition by SHAM can enhance superoxide levels, whereas the AOX inducer pyruvate reduced superoxide levels. Measurement of NO by gas phase chemiluminescence revealed enhanced NO generation in response to NaCl treatment. Upon NaCl treatment there was enhanced tyrosine nitration, which is an indicator of nitrosative stress response. Taken together, our results revealed that AOX induced under salinity stress in germinating chickpea can help in mitigating nitro-oxidative stress, thereby improving germination.

Mitochondrial outer membrane protein MTUS1/ATIP1 exerts antitumor effects through ROS-induced mitochondrial pyroptosis in head and neck squamous cell carcinoma.

We showed that microtubule-associated tumor suppressor gene (MTUS1/ATIP) downregulation correlated with poor survival in head and neck squamous cell carcinoma (HNSCC) patients and that MTUS1/ATIP1 was the most abundant isoform in HNSCC tissue. However, the location and function of MTUS1/ATIP1 have remain unclear. In this study, we confirmed that MTUS1/ATIP1 inhibited proliferation, growth and metastasis in HNSCC in cell- and patient-derived xenograft models in vitro and in vivo. MTUS1/ATIP1 localized in the outer mitochondrial membrane, influence the morphology, movement and metabolism of mitochondria and stimulated oxidative stress in HNSCC cells by directly interacting with MFN2. MTUS1/ATIP1 activated ROS, recruiting Bax to mitochondria, facilitating cytochrome c release to the cytosol to activate caspase-3, and inducing GSDME-dependent pyroptotic death in HNSCC cells. Our findings showed that MTUS1/ATIP1 localized in the outer mitochondrial membrane in HNSCC cells and mediated anticancer effects through ROS-induced pyroptosis, which may provide a novel therapeutic strategy for HNSCC treatment.

An interphase actin wave promotes mitochondrial content mixing and organelle homeostasis.

Across the cell cycle, mitochondrial dynamics are regulated by a cycling wave of actin polymerization/depolymerization. In metaphase, this wave induces actin comet tails on mitochondria that propel these organelles to drive spatial mixing, resulting in their equitable inheritance by daughter cells. In contrast, during interphase the cycling actin wave promotes localized mitochondrial fission. Here, we identify the F-actin nucleator/elongator FMNL1 as a positive regulator of the wave. FMNL1-depleted cells exhibit decreased mitochondrial polarization, decreased mitochondrial oxygen consumption, and increased production of reactive oxygen species. Accompanying these changes is a loss of hetero-fusion of wave-fragmented mitochondria. Thus, we propose that the interphase actin wave maintains mitochondrial homeostasis by promoting mitochondrial content mixing. Finally, we investigate the mechanistic basis for the observation that the wave drives mitochondrial motility in metaphase but mitochondrial fission in interphase. Our data indicate that when the force of actin polymerization is resisted by mitochondrial tethering to microtubules, as in interphase, fission results.

Liver-specific mitochondrial amidoxime-reducing component 1 (Mtarc1) knockdown protects the liver from diet-induced MASH in multiple mouse models.

BACKGROUND: Human genetic studies have identified several mitochondrial amidoxime-reducing component 1 (MTARC1) variants as protective against metabolic dysfunction-associated steatotic liver disease. The MTARC1 variants are associated with decreased plasma lipids and liver enzymes and reduced liver-related mortality. However, the role of mARC1 in fatty liver disease is still unclear. METHODS: Given that mARC1 is mainly expressed in hepatocytes, we developed an N-acetylgalactosamine-conjugated mouse Mtarc1 siRNA, applying it in multiple in vivo models to investigate the role of mARC1 using multiomic techniques. RESULTS: In ob/ob mice, knockdown of Mtarc1 in mouse hepatocytes resulted in decreased serum liver enzymes, LDL-cholesterol, and liver triglycerides. Reduction of mARC1 also reduced liver weight, improved lipid profiles, and attenuated liver pathological changes in 2 diet-induced metabolic dysfunction-associated steatohepatitis mouse models. A comprehensive analysis of mARC1-deficient liver from a metabolic dysfunction-associated steatohepatitis mouse model by metabolomics, proteomics, and lipidomics showed that Mtarc1 knockdown partially restored metabolites and lipids altered by diet. CONCLUSIONS: Taken together, reducing mARC1 expression in hepatocytes protects against metabolic dysfunction-associated steatohepatitis in multiple murine models, suggesting a potential therapeutic approach for this chronic liver disease.

Chang'an decoction alleviates endoplasmic reticulum stress by regulating mitofusin 2 to improve colitis.

OBJECTIVE: To evaluate the protective effects of Chang'an decoction (, CAD) on colitis, and investigate the potential mechanisms underlying these effects from the perspectives of endoplasmic reticulum (ER) stress induced by mitofusin 2 (MFN2). METHODS: The composition of CAD was identified by liquid chromatography-mass spectrometry technology. A mice model of dextran sulfate sodium (DSS) induced colitis was established and therapeutic effects of CAD were determined by detecting body weight, disease activity index, colon length and histopathological changes. Then, the expression levels of MFN2, ER stress markers and Nucleotide-binding domain and leucine-rich repeat protein3 (NLRP3) relevant proteins were detected by polymerase chain reaction (PCR), Western blot, immunohistochemistry and immunofluorescence staining. Subsequently, knockdown and overexpression cell model were constructed to further investigate the underlying mechanism of MFN2 mediating ER stress and energy metabolism by PCR, Western blot, electron microscopy and reactive oxygen species (ROS) staining. Finally, inflammatory indicator and tight junction proteins were measured by PCR and immunofluorescence staining to evaluate the protective effects of CAD. RESULTS: Results showed that the indispensable regulatory role of MFN2 in mediating ER stress and mitochondrial damage was involved in the protective effects of CAD on colitis in mice fed with DSS. Network pharmacology analysis also revealed CAD may play a protective effect on colitis by affecting mitochondrial function. In addition, our data also suggested a causative role for MFN2 in the development of inflammatory responses and energy metabolic alterations by constructing a knockdown and overexpression cell model whereby alter proper ER-mitochondria interaction in Caco-2 cells. Furthermore, relative expression analyses of ER stress markers and NLRP3 inflammasome showed the onset of ER stress and activation of NLRP3 inflammasome, which is consistent with the above findings. In contrast, intervention of CAD could improve the mucosal barrier integrity and colonic inflammatory response effectively through inhibiting ER stress response mediated by MFN2. CONCLUSION: CAD could alleviate ER stress by regulating MFN2 to exert therapeutic effects on DSS-induced colitis, which might provide an effective natural therapeutic approach for the treatment of ulcerative colitis.

Rictor/mTORC2 signalling contributes to renal vascular endothelial-to-mesenchymal transition and renal allograft interstitial fibrosis by regulating BNIP3-mediated mitophagy.

BACKGROUND: Renal allograft interstitial fibrosis/tubular atrophy (IF/TA) constitutes the principal histopathological characteristic of chronic allograft dysfunction (CAD) in kidney-transplanted patients. While renal vascular endothelial-mesenchymal transition (EndMT) has been verified as an important contributing factor to IF/TA in CAD patients, its underlying mechanisms remain obscure. Through single-cell transcriptomic analysis, we identified Rictor as a potential pivotal mediator for EndMT. This investigation sought to elucidate the role of Rictor/mTORC2 signalling in the pathogenesis of renal allograft interstitial fibrosis and the associated mechanisms. METHODS: The influence of the Rictor/mTOR2 pathway on renal vascular EndMT and renal allograft fibrosis was investigated by cell experiments and Rictor depletion in renal allogeneic transplantation mice models. Subsequently, a series of assays were conducted to explore the underlying mechanisms of the enhanced mitophagy and the ameliorated EndMT resulting from Rictor knockout. RESULTS: Our findings revealed a significant activation of the Rictor/mTORC2 signalling in CAD patients and allogeneic kidney transplanted mice. The suppression of Rictor/mTORC2 signalling alleviated TNFα-induced EndMT in HUVECs. Moreover, Rictor knockout in endothelial cells remarkably ameliorated renal vascular EndMT and allograft interstitial fibrosis in allogeneic kidney transplanted mice. Mechanistically, Rictor knockout resulted in an augmented BNIP3-mediated mitophagy in endothelial cells. Furthermore, Rictor/mTORC2 facilitated the MARCH5-mediated degradation of BNIP3 at the K130 site through K48-linked ubiquitination, thereby regulating mitophagy activity. Subsequent experiments also demonstrated that BNIP3 knockdown nearly reversed the enhanced mitophagy and mitigated EndMT and allograft interstitial fibrosis induced by Rictor knockout. CONCLUSIONS: Consequently, our study underscores Rictor/mTORC2 signalling as a critical mediator of renal vascular EndMT and allograft interstitial fibrosis progression, exerting its impact through regulating BNIP3-mediated mitophagy. This insight unveils a potential therapeutic target for mitigating renal allograft interstitial fibrosis.

m6A-methylated Lonp1 drives mitochondrial proteostasis stress to induce testicular pyroptosis upon environmental cadmium exposure.

Cadmium (Cd) is a widely distributed typical environmental pollutant and one of the most toxic heavy metals. It is well-known that environmental Cd causes testicular damage by inducing classic types of cell death such as cell apoptosis and necrosis. However, as a new type of cell death, the role and mechanism of pyroptosis in Cd-induced testicular injury remain unclear. In the current study, we used environmental Cd to generate a murine model with testicular injury and AIM2-dependent pyroptosis. Based on the model, we found that increased cytoplasmic mitochondrial DNA (mtDNA), activated mitochondrial proteostasis stress occurred in Cd-exposed testes. We used ethidium bromide to generate mtDNA-deficient testicular germ cells and further confirmed that increased cytoplasmic mtDNA promoted AIM2-dependent pyroptosis in Cd-exposed cells. Uracil-DNA glycosylase UNG1 overexpression indicated that environmental Cd blocked UNG-dependent repairment of damaged mtDNA to drive the process in which mtDNA releases to cytoplasm in the cells. Interestingly, we found that environmental Cd activated mitochondrial proteostasis stress by up-regulating protein expression of LONP1 in testes. Testicular specific LONP1-knockdown significantly reversed Cd-induced UNG1 protein degradation and AIM2-dependent pyroptosis in mouse testes. In addition, environmental Cd significantly enhanced the m6A modification of Lonp1 mRNA and its stability in testicular germ cells. Knockdown of IGF2BP1, a reader of m6A modification, reversed Cd-induced upregulation of LONP1 protein expression and pyroptosis activation in testicular germ cells. Collectively, environmental Cd induces m6A modification of Lonp1 mRNA to activate mitochondrial proteostasis stress, increase cytoplasmic mtDNA content, and trigger AIM2-dependent pyroptosis in mouse testes. These findings suggest that mitochondrial proteostasis stress is a potential target for the prevention of testicular injury.

Charcot-Marie-Tooth type 2A in vivo models: Current updates.

Charcot-Marie-Tooth type 2A (CMT2A) is an inherited sensorimotor neuropathy associated with mutations within the Mitofusin 2 (MFN2) gene. These mutations impair normal mitochondrial functioning via different mechanisms, disturbing the equilibrium between mitochondrial fusion and fission, of mitophagy and mitochondrial axonal transport. Although CMT2A disease causes a significant disability, no resolutive treatment for CMT2A patients to date. In this context, reliable experimental models are essential to precisely dissect the molecular mechanisms of disease and to devise effective therapeutic strategies. The most commonly used models are either in vitro or in vivo, and among the latter murine models are by far the most versatile and popular. Here, we critically revised the most relevant literature focused on the experimental models, providing an update on the mammalian models of CMT2A developed to date. We highlighted the different phenotypic, histopathological and molecular characteristics, and their use in translational studies for bringing potential therapies from the bench to the bedside. In addition, we discussed limitations of these models and perspectives for future improvement.

VDR restores the expression of PINK1 and BNIP3 in TECs of streptozotocin-induced diabetic mice.

Defective mitophagy in renal tubular epithelial cells is one of the main drivers of renal fibrosis in diabetic kidney disease. Our gene sequencing data showed the expression of PINK1 and BNIP3, two key molecules of mitophagy, was decreased in renal tissues of VDR-knockout mice. Herein, streptozotocin (STZ) was used to induce renal interstitial fibrosis in mice. VDR deficiency exacerbated STZ-induced renal impairment and defective mitophagy. Paricalcitol (pari, a VDR agonist) and the tubular epithelial cell-specific overexpression of VDR restored the expression of PINK1 and BNIP3 in the renal cortex and attenuated STZ-induced kidney fibrosis and mitochondrial dysfunction. In HK-2 cells under high glucose conditions, an increased level of α-SMA, COL1, and FN and a decreased expression of PINK1 and BNIP3 with severe mitochondrial damage were observed, and these alterations could be largely reversed by pari treatment. ChIP-qPCR and luciferase reporter assays showed VDR could positively regulate the transcription of Pink1 and Bnip3 genes. These findings reveal that VDR could restore mitophagy defects and attenuate STZ-induced fibrosis in diabetic mice through regulation of PINK1 and BNIP3.

RNA degradation in human mitochondria: the journey is not finished.

Mitochondria are vital organelles present in almost all eukaryotic cells. Although most of the mitochondrial proteins are nuclear-encoded, mitochondria contain their own genome, whose proper expression is necessary for mitochondrial function. Transcription of the human mitochondrial genome results in the synthesis of long polycistronic transcripts that are subsequently processed by endonucleases to release individual RNA molecules, including precursors of sense protein-encoding mRNA (mt-mRNA) and a vast amount of antisense noncoding RNAs. Because of mitochondrial DNA (mtDNA) organization, the regulation of individual gene expression at the transcriptional level is limited. Although transcription of most protein-coding mitochondrial genes occurs with the same frequency, steady-state levels of mature transcripts are different. Therefore, post-transcriptional processes are important for regulating mt-mRNA levels. The mitochondrial degradosome is a complex composed of the RNA helicase SUV3 (also known as SUPV3L1) and polynucleotide phosphorylase (PNPase, PNPT1). It is the best-characterized RNA-degrading machinery in human mitochondria, which is primarily responsible for the decay of mitochondrial antisense RNA. The mechanism of mitochondrial sense RNA decay is less understood. This review aims to provide a general picture of mitochondrial genome expression, with a particular focus on mitochondrial RNA (mtRNA) degradation.

Pgam5 aggravates hyperglycemia-induced myocardial dysfunction through disrupting Phb2-dependent mitochondrial dynamics.

This study aims to elucidate the roles of Phosphoglycerate Mutase Family Member 5 (Pgam5) and Prohibitin 2 (Phb2) in the context of hyperglycemia-induced myocardial dysfunction, a critical aspect of diabetic cardiomyopathy. The research employed primary cardiomyocytes, which were then subjected to hyperglycemia treatment to mimic diabetic conditions. We used siRNA transfection to knock down Pgam5 and overexpressed Phb2 using adenovirus transfection to assess their individual and combined effects on cardiomyocyte health. Mitochondrial function was evaluated through measurements of mitochondrial membrane potential using the JC-1 probe, and levels of mitochondrial reactive oxygen species (ROS) were assessed. Additionally, the study involved qPCR analysis to quantify the transcriptional changes in genes related to mitochondrial fission and mitophagy. Our findings indicate that hyperglycemia significantly reduces cardiomyocyte viability and impairs mitochondrial function, as evidenced by decreased mitochondrial membrane potential and increased ROS levels. Pgam5 knockdown was observed to mitigate these adverse effects, preserving mitochondrial function and cardiomyocyte viability. On the molecular level, Pgam5 was found to regulate genes associated with mitochondrial fission (such as Drp1, Mff, and Fis1) and mitophagy (including Parkin, Bnip3, and Fundc1). Furthermore, overexpression of Phb2 countered the hyperglycemia-induced mitochondrial dysfunction and normalized the levels of key mitochondrial antioxidant enzymes. The combined data suggest a protective role for both Pgam5 knockdown and Phb2 overexpression against hyperglycemia-induced cellular and mitochondrial damage. The study elucidates the critical roles of Pgam5 and Phb2 in regulating mitochondrial dynamics in the setting of hyperglycemia-induced myocardial dysfunction. By modulating mitochondrial fission and mitophagy, Pgam5 and Phb2 emerge as key players in preserving mitochondrial integrity and cardiomyocyte health under diabetic conditions. These findings contribute significantly to our understanding of the molecular mechanisms underlying diabetic cardiomyopathy and suggest potential therapeutic targets for mitigating myocardial dysfunction in diabetes.

Installation of LYRM proteins in early eukaryotes to regulate the metabolic capacity of the emerging mitochondrion.

Core mitochondrial processes such as the electron transport chain, protein translation and the formation of Fe-S clusters (ISC) are of prokaryotic origin and were present in the bacterial ancestor of mitochondria. In animal and fungal models, a family of small Leu-Tyr-Arg motif-containing proteins (LYRMs) uniformly regulates the function of mitochondrial complexes involved in these processes. The action of LYRMs is contingent upon their binding to the acylated form of acyl carrier protein (ACP). This study demonstrates that LYRMs are structurally and evolutionarily related proteins characterized by a core triplet of α-helices. Their widespread distribution across eukaryotes suggests that 12 specialized LYRMs were likely present in the last eukaryotic common ancestor to regulate the assembly and folding of the subunits that are conserved in bacteria but that lack LYRM homologues. The secondary reduction of mitochondria to anoxic environments has rendered the function of LYRMs and their interaction with acylated ACP dispensable. Consequently, these findings strongly suggest that early eukaryotes installed LYRMs in aerobic mitochondria as orchestrated switches, essential for regulating core metabolism and ATP production.